Many devices, such as high voltage power supplies for x-ray sources, include a power generation circuit that is maintained at a very large electrical potential relative to a grounded metal case and other low electrical potential circuits.
Insulative material, sometimes called “potting”, can be used for insulating circuits at different electric potentials. A problem of very high voltage situations (e.g. ≧1 kilovolt) is breakdown or arcing of the potting. This breakdown might not occur immediately, but may occur many hours after the device is in use, resulting in failure of the device.
One aspect of potting insulative material is that its dielectric strength is typically inversely proportional to its thickness, so a thinner material has a higher dielectric strength per unit distance than a thicker material. This can pose a challenge for applications in which the potting must withstand a very large voltage differential. Two problems resulting from a thicker layer of potting material for larger voltage differentials are (1) the effectiveness of the potting is diminished, because, as mentioned previously, the dielectric strength decreases with increased thickness, and (2) the size and weight of the device is increased. Increased size and weight of the device can be especially detrimental for portable devices, such as portable x-ray sources.